In refrigeration systems, such as cooling systems or air condition systems, the superheat of the refrigerant flowing in the system is often used for controlling the flow of refrigerant through the system. More particularly, a superheat value is often used as a control parameter for controlling an expansion valve arranged in the refrigerant path. Accordingly, it is often desirable to be able to obtain a superheat value for the refrigerant.
U.S. Pat. No. 4,660,387 discloses a control device having a detector for detecting the degree of superheating or supercooling of refrigerating or air-conditioning units. The detector includes a pressure responsive chamber for guiding the pressure of a coolant and a diaphragm disposed therein. The diaphragm is connected with a temperature-responsive cylinder for sensing the temperature of the coolant and a connecting rod. The connecting rod moves corresponding to the pressure and temperature of the coolant, and the position thereof is sensed by a position sensor means.
U.S. Pat. No. 5,070,706 discloses a superheat sensor for sensing the superheat of a fluid flowing through a fluid channel. The superheat sensor includes an aperture within the fluid channel and a sensor body engaging the aperture with a fluid tight seal between the body and the aperture. The sensor body has a sensor body channel in fluid communication with fluid flowing within the fluid channel. A pressure sensor contained within the sensor body has a pressure responsive element in fluid communication with the fluid flowing through the fluid channel for producing an electrical signal representative of pressure of fluid flowing in the fluid channel. A temperature sensor connected to the sensor body has at least one surface in fluid communication with the fluid flowing through the fluid channel for producing an electrical signal representation of temperature of fluid flowing in the fluid channel. A superheat calculator produces a superheat signal in response to the electrical signals representative of pressure and temperature.
U.S. Pat. No. 4,333,317 discloses an automatic control for a refrigeration system for regulating superheat of refrigerant in its gaseous phase existing in the system. The control includes a sensor arranged in thermal control with the system suction line that is divided by a diaphragm into two chambers. One chamber is exposed to suction gas and the other chamber contains a fluid that is essentially the same as the system refrigerant. Mounted on the diaphragm is a four leg strain gage bridge sensor that produces an electrical signal in response to the pressure differential between the chambers.